Aluminum alloy with preferred mechanical property and preferred electrical and thermal conductivity and related manufacturing method

ABSTRACT

Aluminum alloy with preferred mechanical property and preferred electrical and thermal conductivity is provided by a manufacturing method. The aluminum alloy consists of Si about 0.33˜0.37 wt %, Mg about 0.45˜0.55 wt %, and Fe about 0.07˜0.15 wt %, and the rest weight of the aluminum alloy is Al. A ratio of Mg to a different between Al and one third Fe is ranged between 1.45˜1.75.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of 202110926730.4 filed Aug. 12, 2021, the entire disclosure of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The disclosure relates to an aluminum alloy and a related manufacturing method, and more particularly, to an aluminum alloy with preferred mechanical property and preferred electrical and thermal conductivity and a related manufacturing method.

BACKGROUND ART

Aluminum has properties of electrical conductivity and thermal conductivity next only to silver, copper, and gold among metals. Compared with silver, copper and gold, aluminum has advantages of abundant resources, low mining cost, and the preferred electrical conductivity and thermal conductivity per unit weight, and is suitable for manufacturing a lightweight workpiece. Further, aluminum and aluminum alloys can be applied to manufacturing process, forming process and joining process via means to casting, rolling, extruding, forging, drawing, riveting and welding procedures. The aluminum and aluminum alloys can have not only the preferred properties of thermal conductivity, electrical conductivity and non-magnetism, but also the certain mechanical and processing performance for meeting the applicably industrial design requirement. Thus, there are a large number of standards for conductive aluminum alloys, and new conductive aluminum alloys still have been invented. It is difficult to balance high electrical conductivity and high yield strength for the conventional aluminum alloy, which means that the conventional aluminum alloy with the high electrical conductivity has the lower yield strength, and the conventional aluminum alloy with the high yield strength has the lower electrical conductivity. The new electric vehicle industry in Europe and the United States may mix rare earth elements into the aluminum alloy for improving the electrical conductivity and the yield strength, but has drawbacks of expensive cost and manufacturing difficulty.

SUMMARY OF THE DISCLOSURE

The disclosure provides an aluminum alloy with preferred mechanical property and preferred electrical and thermal conductivity and a related manufacturing method for solving above drawbacks.

According to the claimed disclosure, an aluminum alloy with preferred mechanical property and preferred electrical and thermal conductivity includes Si from 0.33 to 0.37 wt %, Mg from 0.45 to 0.55 wt %, Fe from 0.07 to 0.15 wt %. The rest weight of the aluminum alloy is made of Al. A ratio of Mg to a different between Si and one third Fe is ranged between 1.45 and 1.75.

According to the claimed disclosure, the aluminum alloy further includes Ga smaller than or equal to 0.03 wt %, Zn smaller than or equal to 0.03 wt %, Mn smaller than or equal to 0.01 wt %, Ti smaller than or equal to 0.01 wt %, Na smaller than or equal to 0.001 wt %, Li smaller than or equal to 0.0002 wt %, a total of Mn, V and Cr smaller than or equal to 0.015 wt %, and other elements smaller than or equal to 0.01 wt %. The total of above-mentioned elements is smaller than or equal to 0.1 wt %.

According to the claimed disclosure, electrical conductivity of the aluminum alloy is greater than or equal to 34 mS/m, thermal conductivity of the aluminum alloy is greater than or equal to 220 W/m·K, yield strength of the aluminum alloy is greater than or equal to 80 MPa, an elongation rate of the aluminum alloy is greater than or equal to 10%, and hardness of the aluminum alloy is greater than or equal to 40 HBS.

According to the claimed disclosure, a manufacturing method of the aluminum alloy with preferred mechanical property and preferred electrical and thermal conductivity includes melting Al and Si, wherein a weight ratio of Al to Si is preset, melting Mg with a preset weight into combination of Al and Si, and mixing and preserving heat of combination of Mg, Al and Si for centrifugal casting execution or high temperature casting execution so as to acquire the aluminum alloy.

According to the claimed disclosure, the manufacturing method further includes melting the combination of Al and Si with the preset weight ratio at 740˜770 degrees Celsius, detecting and setting Si in a range of 0.33 to 0.37 wt % and Fe in a range of 0.07 to 0.15 wt %, detecting and setting Mg in a range of 0.45 to 0.55 wt %, and detecting and setting a ratio of Mg to a different between Si and one third Fe being ranged between 1.45 and 1.75.

In the disclosure, variations of the mechanical property, the electrical conductivity and the thermal conductivity of the aluminum alloy depend on alloy composition, metallographic structure and alloy cleanness of alloy material. The alloy material has more crystallographic defect, lattice distortion and dislocation resistance are increased accordingly to enhance alloy strength; however, the alloy material may have more structure defects in response to the increased crystallographic defect, and the alloy cleanness being decreased may result in high electron scattering rate, so as to accordingly decrease the electrical conductivity and the thermal conductivity of the alloy material. Thus, the disclosure achieves comprehensive balance between the mechanical property, the electrical conductivity and the thermal conductivity through element composition design and defect control, so as to meet performance requirement of the motor rotor or other applications.

These and other objectives of the disclosure will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an assembling component made by an aluminum alloy according to an embodiment of the disclosure.

FIG. 2 is a flow chart of an aluminum alloy manufacturing method according to the embodiment of the disclosure.

FIG. 3 is a performance diagram of the aluminum alloy according to the embodiment of the disclosure.

DETAILED DESCRIPTION

Please refer to FIG. 1 . FIG. 1 is a diagram of an assembling component 10 made by an aluminum alloy according to an embodiment of the disclosure. The assembling component 10 can be a motor rotor, which include a rotor ring 12, rotor guiders 14 and a rotor axle 16. The rotor ring 12 and the rotor guider 14 can be made by the aluminum alloy of the disclosure, and therefore the aluminum alloy can provide superior performance in mechanical property and electrical and thermal conductivity. It should be mentioned that the aluminum alloy of the disclosure can be used to manufacture the motor rotor and any other type of mechanical workpiece. Any mechanical workpiece of needing the preferred mechanical property and the preferred electrical and thermal conductivity belongs to a scope of the aluminum alloy in the disclosure, and a detailed description is omitted herein for simplicity.

Al (aluminum element) has the preferred electrical and thermal conductivity. The disclosure discloses a manufacturing method of manufacturing the aluminum alloy with the preferred mechanical property, preferred electrical conductivity and preferred thermal conductivity, and the aluminum alloy can be applied for an electric vehicle and any other industry. The aluminum alloy is described herein by a weight percent (wt %) of the total elements within the alloy. The aluminum alloy of the disclosure can include Si about 0.33˜0.37 wt %, Mg about 0.45˜0.55 wt %, and Fe about 0.07˜0.15 wt %; and the rest weight of the aluminum alloy is made of Al. In addition, Si and Mg can be transformed into Mg₂Si, and Mg₂Si can be mixed with Al to generate lattice distortion, so as to further increase mechanical property of the aluminum alloy.

If the aluminum alloy has excess Si element, the electrical conductivity and the mechanical property of the aluminum alloy are decreased accordingly; if Mg in the aluminum alloy is excess, Mg and Al can be transformed into Al₃Mg₂ and the electrical conductivity of the aluminum alloy is decreased accordingly; if Mg₂Si in the aluminum alloy is excess, the electrical conductivity of the aluminum alloy is decreased due to eutectic phase. Thus, the quantity of Si and Mg is strictly constrained to accurately control the preferred electrical conductivity, the preferred thermal conductivity, and the preferred mechanical property of the aluminum alloy. Besides, Al material in crude metal may include Fe, and the quantity of Fe is further constrained to accurately control the quantity and the ratio of Si to Mg.

In the disclosure, Al, Si and Fe can be transformed into AlFeSi in solidifying process of the aluminum alloy, and the rest of Si can be transformed with Mg to generate Mg₂Si, and then the rest of Mg can be transformed into Al₃Mg₂. Therefore, the aluminum alloy and the manufacturing method of the disclosure can accurately set a ratio of Mg to a different between Si and one third Fe conforming to a specific range, which means the quantity of Mg, Si and Fe is decided by Formula 1, so as to effectively avoid the aluminum alloy from having the excess Si element and Al₃Mg₂.

$\begin{matrix} {1.45 \leq \frac{Mg}{{Si} - {{Fe} \times {1/3}}} \leq 1.75} & {{Formula}1} \end{matrix}$

Moreover, the electrical conductivity and the mechanical property of the aluminum alloy may be decreased due to existence of Mn, Ti, Cr, V and other impure elements, so the quantity of the impure elements should be strictly constrained; that is to say, the aluminum alloy may inevitably have oxidized inclusion and porosity drawbacks in melting and casting process due to a mutual effect upon necessary elements and unnecessary elements. A conductive area of the aluminum alloy is decreased due to an electron scattering function resulted from the foresaid drawbacks, which decrease the electrical conductivity and the mechanical property of the aluminum alloy further, so that the quantity and percentage of the impure elements in the aluminum alloy are strictly constrained.

The necessary elements of the aluminum alloy in the disclosure preferably can include Si about 0.33˜0.37 wt %, Mg about 0.45˜0.55 wt %, Fe about 0.07˜0.15 wt %, and the rest weight of the aluminum alloy is made of Al; the quantity of Mg, Si and Fe can conform to Formula 1. The impure elements of the aluminum alloy can include Ga equal to or smaller than 0.03 wt %, Zn equal to or smaller than 0.03 wt %, Mn equal to or smaller than 0.01 wt %, Ti equal to or smaller than 0.01 wt %, Na equal to or smaller than 0.001 wt %, Li equal to or smaller than 0.0002 wt %, a total of Mn, V and Cr equal to or smaller than 0.015 wt %, and other elements equal to or smaller than 0.01 wt %; a total percent of foresaid elements in the aluminum alloy can be equal to or smaller than 0.1 wt %.

Please refer to FIG. 2 . FIG. 2 is a flow chart of an aluminum alloy manufacturing method according to the embodiment of the disclosure. The aluminum alloy manufacturing method illustrated in FIG. 2 can be suitable for the aluminum alloy and the assembling component 10 shown in FIG. 1 . The aluminum alloy manufacturing method can execute step S100 to melt metal aluminum and crystalline silicon inside a container at 740˜770 degrees Celsius; step S100 can preset a weight ratio of Al to Si. Then, step S102 can be executed to detect and adjust the aluminum alloy inside the container including Si about 0.33 to 0.37 wt % and Fe about 0.07˜0.15 wt %, and further confirm other impure elements conforming to the above-mentioned condition.

Then, step S104 and step S106 can be executed to mix non-polluted salt scouring agent into the container for deslagger execution, and melt Mg with a preset weight into the container. Content of the scouring agent and the related deslagger execution can depend on a design demand, and a detailed description is omitted herein for simplicity. The quantity of Mg melted in step S106 can conform to the preset weight, and further conform to the foresaid ratio of Mg to the different between Si and one third Fe, which means Formula 1. In the meantime, step S108 can be optionally executed to detect and set the aluminum alloy including Mg about 0.45˜0.55 wt %, and the ratio of Mg to the different between Si and one third Fe ranged between 1.45 and 1.75.

Then, step S110 can be executed to aerate inert gas into the container for degassing execution. The inert gas may be nitrogen gas, argon gas or other applicable gas, which depends on the design demand. In the disclosure, porosity degree of the aluminum alloy after the degassing execution can conform to Level 2 or higher level of Metallographic of cast aluminum alloys (JB/T7946.3) published as machinery industry standard (People's Republic of China, RPC), or decompression solidification density of the aluminum alloy in a decompression condition can be greater than 2.67 g/cm³, or a ratio of a difference between atmospheric solidification density and the decompression solidification density to the atmospheric solidification density in an atmospheric condition can be smaller than 1.5, or hydrogen content of molten aluminum of the aluminum alloy can be smaller than 0.2 ml/100 gAl and liquid permeability of the aluminum alloy can be greater than or equal to 500 g/min. Final, step S112 can be executed to mixing and preserving heat of the aluminum alloy in a liquid state for centrifugal casting execution or high temperature casting execution, so as to form the ingot, the stick or any other type by the aluminum alloy, such as the motor rotor of the assembling component 10.

After step S112, if the cast ingot and/or the cast stick is melted for reproduction, the liquid aluminum alloy still has to conform to the foresaid quantity of Si, Mg and Fe, and the foresaid ratio of Mg to the different between Si and one third Fe, and a cooling rate of the aluminum alloy in casting execution can be ranged between 1˜100 Celsius degrees per second, so that the aluminum alloy can provide the preferred mechanical property, the preferred electrical conductivity and the preferred thermal conductivity. As if the motor rotor of the assembling component 10 is cast via step S112, a temperature of the motor rotor in hot installation process can be set as 200˜350 degrees Celsius, and a thermal insulation period of the motor rotor in the hot installation process can be set between 15˜60 minutes. Therefore, the aluminum alloy manufactured by the manufacturing method of the disclosure can have the electrical conductivity greater than or equal to 34 mS/m, and further have the thermal conductivity greater than or equal to 220 W/m·K, and further have the yield strength greater than or equal to 80 MPa, and further have the elongation rate greater than or equal to 10%, and further have the hardness greater than or equal to 40 HBS.

Table 1 discloses several sampling examples of the motor rotor of the assembling component 10, which conforms to the foresaid element quantity and ratio, and further discloses testing results of the electrical conductivity, the thermal conductivity, the mechanical property, metallographic analysis and grain-size analysis of each sampling example. The aluminum alloy made by the manufacturing method of the disclosure can have advantages of the preferred mechanical property, the preferred electrical conductivity and the preferred thermal conductivity. Density equivalent disclosed in Table 1 can be interpreted as the foresaid ratio of the difference between the atmospheric solidification density and the decompression solidification density to the atmospheric solidification density in the atmospheric condition.

TABLE 1 Item Example 1 Example 2 Example 3 Example 4 Alloy Mg (wt %) 0.453 0.552 0.545 0.461 composition Si (wt %) 0.334 0.365 0.371 0.363 Fe (wt %) 0.074 0.146 0.081 0.135 Mg/(Si—1/3Fe) 1.46 1.74 1.58 1.45 Ga (wt %) 0.015 0.027 0.019 0.023 Zn (wt %) 0.018 0.024 0.009 0.012 Mn (wt %) 0.009 0.002 0.003 0.003 Mn + V + Cr 0.014 0.010 0.008 0.010 (wt %) Ti (wt %) 0.005 0.009 0.008 0.008 Na (wt %) 0.0002 0.0005 0.0009 0.0003 Li (wt %) 0.0001 0.0002 0.0001 0.0001 other elements ≤0.01 ≤0.01 ≤0.01 ≤0.01 (wt %) Total of impure ≤0.1 ≤0.1 ≤0.1 ≤0.1 elements (wt %) Al the rest the rest the rest the rest Gas content Porosity degree — Level 1 Level 2 — Decompression 2.672 — — 2.681 solidification density (g/cm³) Density — — — — equivalent(%) Hydrogen — — — — content(ml/100 g) Slag Liquid 536 — 552 520 content permeability (g/min) Mechanical Yield strength 86 102 93 89 property (MPa) Elongation rate 21.3 17.8 18.5 19.6 (%) Hardness (HB) 42.6 46.7 45.3 44.8 Electrical conductivity (MS/m) 35.2 34.2 34.6 34.5 Thermal conductivity 227 221 223 223 (W/(m · K)) Item Example5 Example6 Example7 Example8 Example9 Alloy Mg (wt %) 0.543 0.457 0.539 0.459 0.511 composition Si (wt %) 0.342 0.338 0.336 0.359 0342 Fe (wt %) 0.095 0.139 0.082 0.125 0.117 Mg/(Si—1/3Fe) 1.75 1.57 1.75 1.45 1.69 Ga (wt %) 0.014 0.026 0.018 0.023 0.021 Zn (wt %) 0.019 0.009 0.013 0.027 0.025 Mn (wt %) 0.004 0.003 0.003 0.002 0.003 Mn + V + Cr 0.012 0.009 0.008 0.007 0.007 (wt %) Ti (wt %) 0.007 0.005 0.008 0.006 0.007 Na (wt %) 0.0006 0.0004 0.0008 0.0005 0.0005 Li (wt %) 0.0002 0.0002 0.0001 0.0001 0.0001 other elements ≤0.01 ≤0.01 ≤0.01 ≤0.01 ≤0.01 (wt %) Total of impure ≤0.1 ≤0.1 ≤0.1 ≤0.1 ≤0.1 elements (wt %) Al the rest the rest the rest the rest the rest Gas content Porosity degree — — — — — Decompression — — — — 2.682 solidification density (g/cm³) Density 0.9 — — 1.4 — equivalent(%) Hydrogen — 0.18 0.14 — — content(ml/100 g) Slag Liquid — — — — 518 content permeability (g/min) Mechanical Yield strength 95 93 99 88 96 property (MPa) Elongation rate 18.8 19.2 17.5 18.0 19.5 (%) Hardness (HB) 43.5 43.1 44.0 44.6 45.9 Electrical conductivity (MS/m) 34.8 34.6 34.5 34.7 34.9 Thermal conductivity 222 225 221 223 224 (W/(m · K))

Please refer to FIG. 3 . FIG. 3 is a performance diagram of the aluminum alloy according to the embodiment of the disclosure. As shown in FIG. 3 , a marking frame F3 can represent the conventional aluminum alloy with high yield strength and low electrical conductivity, such as A356-T6 and A356+0.5Cu-T6; a marking frame F4 can represent the conventional aluminum alloy with high electrical conductivity and low yield strength, such as Al99.7 (99.7 wt % Al) and Al99.5 (99.5 wt % Al); a marking frame F1 can represent the aluminum alloy including Ni in the range of 4.3 to 6 wt %, which has high manufacturing cost and medium yield strength and medium electrical conductivity, is disclosed in WO 2020/028730; a marking frame F2 can represent the aluminum alloy of the disclosure, which has the yield strength and the electrical conductivity better than the aluminum alloy of the frame F1.

In conclusion, variation of the mechanical property, the electrical conductivity and the thermal conductivity of the aluminum alloy depend on alloy composition, metallographic structure and alloy cleanness of alloy material. The alloy material has more crystallographic defects, lattice distortion and dislocation resistance are increased accordingly to enhance alloy strength; however, the alloy material may have more structure defect in response to the increased crystallographic defect, and the alloy cleanness being decreased may result in high electron scattering rate, so as to accordingly decrease the electrical conductivity and the thermal conductivity of the alloy material. Thus, the disclosure achieves comprehensive balance between the mechanical property, the electrical conductivity and the thermal conductivity through element composition design and defect control, so as to meet performance requirement of the motor rotor or other applications.

Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the disclosure. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims. 

What is claimed is:
 1. An aluminum alloy with preferred mechanical property and preferred electrical and thermal conductivity, comprising: Si from 0.33 to 0.37 wt %; Mg from 0.45 to 0.55 wt %; Fe from 0.07 to 0.15 wt %; and Al, wherein the rest weight of the aluminum alloy is made of Al.
 2. The aluminum alloy of claim 1, wherein a ratio of Mg to a different between Si and one third Fe is ranged between 1.45 and 1.75.
 3. The aluminum alloy of claim 1, further comprising: Ga smaller than or equal to 0.03 wt %; Zn smaller than or equal to 0.03 wt %; Mn smaller than or equal to 0.01 wt %; Ti smaller than or equal to 0.01 wt %; Na smaller than or equal to 0.001 wt %; Li smaller than or equal to 0.0002 wt %; a total of Mn, V and Cr smaller than or equal to 0.015 wt %; and other elements smaller than or equal to 0.01 wt %; wherein a total of above-mentioned elements is smaller than or equal to 0.1 wt %.
 4. The aluminum alloy of claim 1, wherein electrical conductivity of the aluminum alloy is greater than or equal to 34 mS/m, thermal conductivity of the aluminum alloy is greater than or equal to 220 W/m·K, yield strength of the aluminum alloy is greater than or equal to 80 MPa, an elongation rate of the aluminum alloy is greater than or equal to 10%, and hardness of the aluminum alloy is greater than or equal to 40 HBS.
 5. A manufacturing method of an aluminum alloy with preferred mechanical property and preferred electrical and thermal conductivity, comprising: melting Al and Si, wherein a weight ratio of Al to Si is preset; melting Mg with a preset weight into combination of Al and Si; and mixing and preserving heat of combination of Mg, Al and Si for centrifugal casting execution or high temperature casting execution so as to acquire the aluminum alloy.
 6. The manufacturing method of claim 5, further comprising: melting the combination of Al and Si with the preset weight ratio at 740770 degrees Celsius.
 7. The manufacturing method of claim 5, further comprising: detecting and setting Si in a range of 0.33 to 0.37 wt % and Fe in a range of 0.07 to 0.15 wt %.
 8. The manufacturing method of claim 7, further comprising: detecting and setting Mg in a range of 0.45 to 0.55 wt %; and detecting and setting a ratio of Mg to a different between Si and one third Fe being ranged between 1.45 and 1.75.
 9. The manufacturing method of claim 5, further comprising: mixing salt scouring agent into the foresaid combination for deslagger execution; and aerating inert gas into the foresaid combination for degassing execution.
 10. The manufacturing method of claim 9, wherein porosity degree of the aluminum alloy after the degassing execution conforms to Level 2 or higher level of Metallograph of cast aluminum alloys (JB/T7946.3) published as machinery industry standard (People's Republic of China, RPC), or decompression solidification density of the aluminum alloy in a decompression condition is greater than 2.67 g/cm³, or a ratio of a difference between atmospheric solidification density and the decompression solidification density to the atmospheric solidification density in an atmospheric condition is smaller than 1.5, or hydrogen content of molten aluminum of the aluminum alloy is smaller than 0.2 ml/100 gAl and liquid permeability of the aluminum alloy is greater than or equal to 500 g/min.
 11. The manufacturing method of claim 5, further comprising: setting a cooling rate of the aluminum alloy in casting execution ranged between 1˜100 Celsius degrees per second.
 12. The manufacturing method of claim 5, further comprising: forming a motor rotor by the aluminum alloy; and setting a temperature of the motor rotor at 200˜350 degrees Celsius in hot installation process, and a thermal insulation period in the hot installation process being set between 15˜60 minutes. 